BIOREACTOR AND MICROORGANISM ACTIVATING METHOD

PROBLEM TO BE SOLVED: To enhance wastewater treatment capacity and the holding capacity of activated sludge by making a flow velocity uniform and proper and to promote the miniaturation of an apparatus. SOLUTION: An oxygen supply device 4 arranged to the lower part of an aeration region 5 to supply air into a liquid to be treated and a microorganism carrier group arranged in a reaction region and formed from a plurality of microorganism carrier elements are provided. The microorganism group is divided into a first microorganism carrier element 3-1 nearer to an aeration region 5 and a second microorganism carrier element 3-2 remote from the aeration region 5. The upper end of the first microorganism carrier element 3-1 is set to a position lower than the upper end of the second microorganism carrier element 3-2. The upper part of rising stream 31 rising while being induced by the rising of oxygen bubbles revolves at the upper end of the first microorganism carrier element 3-1 to be converted to a horizontal stream to receive resistance at the side surface of the second microorganisms carrier element 3-2 to flow in the gap formed between both elements to form two kinds of falling flows (a), (b). The presence of the defference in levels of both elements equalizes the speeds of the falling flows (a), (b) to enhance wastewater treatment capacity.